Use an anti corrosive paint for protecting steel structures

An anti corrosion coating (anti corrosive paint) acts as a barrier between a metal and its environment, and increases its durability and lifespan. The roughly estimated global cost of metal corrosion damage is trillions of dollars. The good news is that a lot of this loss can be prevented by being proactive and making the right choice of anti corrosion solution from the start.

To determine the best anti corrosive paint for your project, it is important to factor in the environment and type of metal. Whether corrosion is due to moisture, chemicals, salt spray, or oxidation, anti rust coating for steel and metal can help protect the substrate from the elements.

The best anti corrosion paint meets the requirements of the corrosion category

To determine the best anti corrosive paint for your project, you need to understand the environment and use of the substrate. Particularly its exposure to water, moisture, and other aggressive substances that might be present in the environment. The corrosivity of certain atmospheres has been classified and standardised by the International Organisation for Standardisation. The standard divides the degree of corrosivity into 5 categories , C1 to C5, in order of increasing corrosivity. To find the right anti corrosion solution, you need to know how corrosive the environment will be. For example, a coating at C5M level is intended for offshore constructions (like the coastal areas of Australia) which are constantly exposed to moisture, but also for small pipes that are equally exposed.

Anti corrosive paint must be chosen based on the environment: here a C5 anti rust paint would have been needed.

Keep in mind that for categories C4-C5 it is not recommended to apply the anti corrosive paint yourself. Please search out a specialist in that case.

Once you have determined the corrosivity of your environment, you can identify the right coating systems for your project and the right anti corrosive paint specification to protect it for years to come. Following these guidelines will allow you to pick an appropriate anti corrosive paint, allowing you to avoid overspending on unnecessary degrees of protection or simply making the wrong choice of anti rust solution.

The types of anti corrosive paints

Generally, the types of anti corrosive paints can be divided into three categories:

Galvanic coatings/Cathodic protection (C3 – C5) – metal-rich coatings (metal paint coating) which provide a sacrificial layer. Prevents corrosion by providing a more easily corroded metal (such as zinc) to be the anode to the protected metal’s cathode. Also called the sacrificial anode, this metal will corrode instead of the protected metal.For example: hot dip galvanizing which provides steel (cathode) with a layer of zinc (anode).

Inhibitor coatings (C1 – C4) – release a chemical which interferes with the electrolyte and stops the corrosion process.For example: all oil based coatings with corrosion inhibitor additives such as zinc, aluminium, zinc oxide and so on.

Apply metal paint coating by dipping or spraying

The two most common methods for applying an industrial grade anti rust coating for steel are hot dip galvanising and thermal (metal) spraying. Barrier coatings and corrosion inhibitor coatings can also be applied by spraying or dipping.

Thermal spraying applies zinc or aluminium to a substrate by taking the metal in the form of a powder or wire and feeding it into a special spray gun. The metal melts within the gun and can then be sprayed onto the substrate. It does not alloy, but instead works by coating the surface in overlapping metal platelets.

Hot Dipping is the process of immersing a metal in a bath of metal, often molten zinc,(or a polymer) in order to form a coating. The liquid metal bonds to the substrate and forms an alloy, which is then coated in zinc as it is removed from the bath. Hot dip galvanising uses the principle of cathodic protection, as the zinc coating acts as an anode to its substrate.

More than a rust solution – the benefits of anti corrosion coatings

The most common anti corrosion solution is ‘anti rust paint’, essentially the collective name for various products used for coating metal to prevent rust. An anti corrosion solution can do more than just protect from corrosion, and its multi functional nature means that it is possible to find the exact coating your project requires. Corrosion is caused by a chemical reaction between a metal and its environment (water or other fluids or prolonged exposure to UV radiation), typically producing an oxide or a salt of the original metal. The long and the short of it is the metal is weakened, as is the structure it creates. An anti rust solution prevents direct contact between water/fluids and the steel substrate and therefore prevents the corrosion process.

In general anti corrosion coating is suitable for almost any type of steel and metal, and has the following 5 benefits:

The best anti rust coating for steel is a Duplex anti rust solution

When hot dip galvanising is used together with a top coat of anti corrosive paint or a layer of powder coating, it is known as a Duplex System.

This anti rust coating for steel provides multiple types of protection and the longest-lasting results. Each layer needs to be compatible in order for the system to work effectively. It is especially suitable for corrosion categories C3 to C5 and looks like this:

Primer: hot dip galvanisation OR applying an inhibitor coating primer depending on the coating system of your choice.

Sealer: To seal the anti corrosive paint. Often epoxy based.

Intermediate coat: there may be several layers necessary for optimum protection, depending on the corrosion category.

Top coat: provides appearance and surface resistance, often first line of defence.

Even though duplex systems are considered the best corrosion protection for steel, they are not suitable for all applications. For example, they are not common in preserving components of industrial machinery. For this purpose innovative solutions are being developed, to prevent corrosion eating away at Australian industry.

For smaller substrates or do it yourself application up to category C2, painting at home is also an option. There is anti corrosion spray available for this purpose. An anti corrosion spray can be described as an ultra thin fluid film compound used for spray coating metal to prevent rust. In spray form it can protect for up to a year. Keep in mind that more exposed areas which are getting constant abuse from rain and salt will need spraying regularly. In paint form, longer lasting results can be accomplished depending on the coating system you choose. For the best result always opt for a two component coating with corrosion inhibitor additives, for example a zinc rich epoxy coating. Such products include Wattyl Killrust product line from Sherwin Williams.

Find an anti corrosion paint specialist in Australia

If you are looking for a professional company to apply anti rust paint for you, it’s important to understand how prices are established before you request a quote. Different coating processes use different methods to calculate the cost of professional application. Hot dip galvanising prices are usually calculated by weight. The galvaniser will quote a price per tonne, and then use the weight of your steelwork after galvanising to calculate the final cost. Unlike galvanising, powder coating prices tend to be calculated by size or surface area.

Regional differences in materials, labour, and equipment can all have an impact on overall costs when contracting a coating expert. If you want to receive a custom made quote, please contact us.

Here are a few examples of local anti corrosive paint specialists in Australia:

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